Using solar to charge Tesla S in Switzerland

[T in Geneva]

Hello, I have day/night tariff so charge my Tesla S P85D and my Tesla 3 at night.

I am considering installing solar panels and charge for free during the day, but am concerned that the solar panels at 9.84 KWC will not provide enough power to charge my cars during the day, and that I will end up "topping up" during the day at a substantially higher electricity price than my current set up charging at night. I am NOT putting in a battery for my solar installation.

Does anyone have any experience ? how do I do the maths of translating solar power to charging power for the cars ?

Thanks.

 

[EVRider-FL]

I don’t know the calculation, but I suspect your panels would not generate enough energy to charge your car, especially if you’re using solar for other energy consumers in your home. Consider what you’re trying to accomplish to see if the investment in solar is worthwhile financially.

 

[ewoodrick]

Hello, I have day/night tariff so charge my Tesla S P85D and my Tesla 3 at night.

I am considering installing solar panels and charge for free during the day, but am concerned that the solar panels at 9.84 KWC will not provide enough power to charge my cars during the day, and that I will end up "topping up" during the day at a substantially higher electricity price than my current set up charging at night. I am NOT putting in a battery for my solar installation.

Does anyone have any experience ? how do I do the maths of translating solar power to charging power for the cars ?

Thanks.

You can't really "dedicate" solar for charging the car unless it is on a circuit all by itself.
And solar by itself and charging a Tesla doesn't really go well together.

How much the car needs depends on how much you drive it.

 

[livesmith]

Hello, I have day/night tariff so charge my Tesla S P85D and my Tesla 3 at night.

I am considering installing solar panels and charge for free during the day, but am concerned that the solar panels at 9.84 KWC will not provide enough power to charge my cars during the day, and that I will end up "topping up" during the day at a substantially higher electricity price than my current set up charging at night. I am NOT putting in a battery for my solar installation.

Does anyone have any experience ? how do I do the maths of translating solar power to charging power for the cars ?

Thanks.

I'm not entirely sure what KWC is. Usually it would be KW for Kilowatts.
Then it's a matter of what power your solar is actually outputting and how much charge you need to put back into your cars...

So... As a rough idea... My 15' 85D currently has about 60KWH of capacity. So if I bring it home with maybe less than 20% and then charge to 100% in the morning, I add about 50KWH.

So, IF your solar was actually full sun and actually outputting 10KW, then it would take 5 hours to put that much charge back into the car charging at 10KW...

If you want better numbers, I think you'd do well to use something like Tessie and log how much power and time and total KWH you are putting into your vehicles.

You'll have to do more solar research as to how much power you are actually putting out and for how long and then try to factor in the seasonal changes and rainy days, etc... Solar installers should have something like this.(hopefully they are somewhat accurate and not just trying to sell you...)

 

[livesmith]

Hello, I have day/night tariff so charge my Tesla S P85D and my Tesla 3 at night.

I am considering installing solar panels and charge for free during the day, but am concerned that the solar panels at 9.84 KWC will not provide enough power to charge my cars during the day, and that I will end up "topping up" during the day at a substantially higher electricity price than my current set up charging at night. I am NOT putting in a battery for my solar installation.

Does anyone have any experience ? how do I do the maths of translating solar power to charging power for the cars ?

Thanks.

I think the closest you can come to this is going to be playing with your installation and possibly turning down charging speeds to try to keep it under your solar output... Or *possibly* playing with something like Tessie and IFTTT or otherwise trying to set up some sort of routine that watches solar output and adjusts charging speeds... I'm not entirely sure just what it would take to do that...

 

[ewoodrick]

I think the closest you can come to this is going to be playing with your installation and possibly turning down charging speeds to try to keep it under your solar output... Or *possibly* playing with something like Tessie and IFTTT or otherwise trying to set up some sort of routine that watches solar output and adjusts charging speeds... I'm not entirely sure just what it would take to do that...

I don't think that the car would do well on a solar only solution.
For example, in the morning, the circuit comes alive and the car starts to draw power, but the cells aren't generating enough for 32A yet. Maybe the car would crank the charge down to minimum, but it won't then crank it back up.

 

[livesmith]

I don't think that the car would do well on a solar only solution.
For example, in the morning, the circuit comes alive and the car starts to draw power, but the cells aren't generating enough for 32A yet. Maybe the car would crank the charge down to minimum, but it won't then crank it back up.

It would have to be programmed to come back up. It doesn't look like Tessie currently supports charging amperage changes. Though I could picture some ugly fake human scripting too do it.
Obviously the better Way to do it would be with actual scripting through better sources than I am currently familiar with myself.

 

[ewoodrick]

It would have to be programmed to come back up. It doesn't look like Tessie currently supports charging amperage changes. Though I could picture some ugly fake human scripting too do it.
Obviously the better Way to do it would be with actual scripting through better sources than I am currently familiar with myself.

No, it really can't be done with anything. What if a cloud passes over? The charger is basically going to be clicking it's head off!

The correct ways to do it, AFAIK:

1. Hook the solar to the house and configure it to offset home usage.
2. Add a LOT of batteries

As nice as it sounds to charge your car off of solar, it's a real PITA to do so. The only option is to basically offset your electric bill so that you don't see the car charging.

And I hate this concept of "charge for free" with solar. Sure, for a simple $20k investment, I don't have to pay monthly.

But wait, you're going to finance the $20k? Then you are back to paying monthly.

But in 15-20 years, it may be free. (assuming that you don't have to replace the cells)

 

[livesmith]

No, it really can't be done with anything. What if a cloud passes over? The charger is basically going to be clicking it's head off!

The correct ways to do it, AFAIK:

1. Hook the solar to the house and configure it to offset home usage.
2. Add a LOT of batteries

As nice as it sounds to charge your car off of solar, it's a real PITA to do so. The only option is to basically offset your electric bill so that you don't see the car charging.

And I hate this concept of "charge for free" with solar. Sure, for a simple $20k investment, I don't have to pay monthly.

But wait, you're going to finance the $20k? Then you are back to paying monthly.

But in 15-20 years, it may be free. (assuming that you don't have to replace the cells)

I believe it could be done but yeah, I'm not aware of any easy way.

Yes as far as getting solar it all comes down to what you pay for electricity and what you're paying for the solar and how much actual generation you get. Everywhere is different.

I did a quick glance the other day with my rate of about 10 cents per kwh in upstate NY and the cheapest diy kit that popped up and at the moment it was looking at like around 10 years to pay back.

 

[KalJoMoS]

Hello, I have day/night tariff so charge my Tesla S P85D and my Tesla 3 at night.

I am considering installing solar panels and charge for free during the day, but am concerned that the solar panels at 9.84 KWC will not provide enough power to charge my cars during the day, and that I will end up "topping up" during the day at a substantially higher electricity price than my current set up charging at night. I am NOT putting in a battery for my solar installation.

Does anyone have any experience ? how do I do the maths of translating solar power to charging power for the cars ?

Thanks.

Well it all depends how much is the average usage of your household during the time you want to charge your car. Is the day/night tariff time of change usable in the solar production of your setup? And do you use Tesla HPWC to charge your car?
Overall answer would be yes, it’s possible. As others have noted you will get the solar power at around 9 o’clock during summer and most of it at noon. If your daily schedule is accordingly then you’re all set. But during winter you need to rely on the day/night tariff as now.
I have this similar setup, my solar panels provide app. 8.8 kWh in production but this is in very specific time of the year. And only thing that is Tesla, beside the car is HPWC. So you are not limited to the hardware. I believe Tesla is only selling their system with Powerwall battery’s so there is the decision point as well. If able to select, then it’s recommended. Do know that other companies prowide same kind of products.
That Tesla HPWC is unique in way that you can configure it during installation on how high is the power consumption (can’t say the same for other products). I have 16A braker on the connector and have dialled it down to 8A, so that the overall consuption with my household does not trip it. In the real life it’s providing half of the maximum available so I will get approximately 23km per hour on my Model S. Fair enough with my drive’s. Also a note that current car’s software is now allowing to set desired voltage of each of your charge. Previously it was not there.
If you choose to get the system with batteries, then they might help a bit but not much. As in reality you would need the battery supply if you need to charge your car and there is no sun for it, right? Then you would need to charge the batteries from grid to be able to provide their power for your load. But this would be at the same time that you’re currently using to charge your car’s, wouldn’t? So it’s all about decisions.
I use it and it’s nice to have that function. That 8A power is approximately 5.5kWh on 3phase load.